Drying-kiln.



E. E. PERKINS.

' DRYING KILN. APPLICATION FILED MAR. 19. 1917.

In: mum: frills m, Florin-1N0. Ilusnlnmu". D. c.

through the fiues.

- r TED STATES PATEN'roFFIo ELM-ER E. PERKI S, or CHICAGO, i'LLINoI's.

DRYING-K1111.

Specification of Letters 2mm.

Patented Jan. 7; 1919.

Applicatibn filed March 19, 1917. 'SerialNo. 155,712.

To allfw'hom it 0mm:

Be it known that LEL ER PERKINS, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Drying-Kilns,of which the following is a specification.

This invention relates infgeneral to drying kilns and has more particularreference tothat type of kiln which is employed for drying lumber by what is called the open, "or moist air, process.

These kilns are fcustomarily provided with heat insulated walls but the inlet and outlet flues for the kiln have been located within the walls themselves; The result of this construction is that the moisture within the kiln will feed by capillary attraction'through the walls where they are joined by these flues, thus not only depriving the kilnofthe necessary moisture but also eventually destroying the structure of the wall. Furthermore, since the temperature of the outer'wall of the kiln structure is usually considerably less than the inner wall it necessarily follows that the temperature within both the inlet and outlet fines will be less than the temperature inside the kiln, and consequently, variations in the outside temperature will materially affect the circulation of air It sometimes happens that the temperature of the inlet flues becomes higher than the temperature of the outlet lines, with the result that'circulation in the kiln is entirely stopped or sometimes it is even reversed so that the air flows in through the outlet flues and out through the inlet Hues. To overcome this difliculty encountered in the operation of the kilns it has heretofore been proposed to heat the air in the outlet flues by means of steam pipes disposed Within these outlet flues, so that the air in the flues will be heated and caused to rise, thereby drawing the air from the interior of the kiln and establishing the requisite circulation.

One of theprimary obiects of'mv present invent on is to obviate all of the difficulties heretofore encountered, by reason of the location of the inlet and outlet flues in the hollow walls of the kiln structure, and with this end inview I propose to arrange both the inlet and outlet fiues within the kiln or drying room itself where they are uninfluenced By variations in outside temperature.

Another object r my invention is a insure outliow of air through the outlet flues without resorting to steam' pipes or other heating means Witlliil the flues, the outflow in the present instance being maintained by atmospheric conditions within the kiln itself.

A further object is to provide a kiln in which the circulation can be regulated and controlled at will, and so constructed that the circulationmay be entirely shut off until the material to be dried has been heated and steamed to the requisite degree, whereupon the circulation may beestablished within the kiln to produce the desired moistair drying and finally the circulation maybe increased so as to permit-"the material to cool in such a Way that all stresses and strains are re moved from the-material before the material is takenI'out. v 1

Still another object is to so "construct and arrange the air intake flue to the :kiln that the air will be thoroughly distributed and uniformly delivered to the kiln throughout its entire length so as to result in a uniform drying of all the material in the kiln. Other 'ObjBCtS'fllld advantages of my 'pres ent inventionwill be-readily appreciated by those skil ed in the art as thesame becomes better under tood by reference to the following description when considered in conrection with the accompanying sheet of drawings. i

Referring to the drawings, the single figure shows a per pective view of the interior of a kiln embodying my invention.

On the drawings. reference characters 3 and 4 indica e the s de walls of my kiln, and 5 and 6 the floor and ceilinq'respe'ctivelv. all of the Walls beinepreferably constructed to provide suitable dead airspaces so that the room wi l be adequately heat-in ulated to prevent dissip tion and loss of heat from the interior of the k ln.

Aplurality of tracks 7. preferably three in number. are-suppor ed approx mately two and one-half feet above the floor 5 upon suitable supporting columns '8. these tracks being adap ed to supportthe lumb'er or other materialto be dried; which may be piled d rectly upon the tracks or.'as iscustomarily done, it i'nay be ruii'into the room upon trucks or car bunks constructed to tra el upon these tracks.

Uponthecolnmns 8 beneath the tracks "aresecurely mounted a se'ries of transversely extending beams or channel bars 9 which serve as supports for the heating pipes 11, preferably arranged in sections and connected at their ends with header-"pipes 12, steam being supplied to the headers at on end through supply pipes 13 and exhausted from the other end through the delivery pipes 140 For the'purpose of producing the requisite humidity within the kiln I employ a steam-spraying pipe 15, of any preferred constructiompthrough which steam -1s adair may be controlled; By locating the intake flue within the kiln itself instead of within the hollow side-walls, the flue isnot affected by outside temperature changes,and furthermore, theheatinsul'ating properties of the side walls are not impaired nor is there any solid connection between the inner and outer wall through whlch moisture can escape from the kiln by capillary action so as to impair the efficiency of the kiln'or injure the structure of the side-walls."

For the purpose of insuring aneven distribution of the 'inflowing airthroughout the length of the kiln-the flue '16 provided with a plurality of upwardly extendingdelivery branches 19, 21, 22-and 28 respec "i0 tively, which, as will be seen from the drawings, increase in length from the intake end of the'flue 16. Since the air in the kiln'is cooler at the bottom than it is nearer the top it" will be obvious that'the longer delivery branches will be heated to' a higher temperature by the surrounding air within the kiln thantheshorter branches. Consequently, a greater draft willbe created by the longer branches, but since the longer branches are more remote from the intake end of the flue it will be obvious that this increased draft will bebal'anced by the tendency of the air to escape through the firstbranches encountered in its passage through the flue, Wlth the result that the air will be delivered from all of the branches in substantially equal amounts,vso that uniform distribution through the kiln is secured, which results in uniform drying of all of the material. 7

The air is permitted to escape from the kiln so as to maintain the requisite circulation therein through a plurality ofoutlet flues, designated generallyby reference character 2 1. These flues extend directly through the iceilingwof' theflroom sand, eare-. preferably equipped at their upper delivery'ends with caps or Windshields 25 and also provided outside the kiln itself with valves or dampers 26, by means of which the flow of air through the flues may be controlled or shut ofi as occasion requires. It will be observed that these flues instead of being disposed within the hollow side-walls of the kiln project directly downwardly into the kiln itself so that they are entirely surrounded by the air within the kiln and are subjected ;to the temperatures of the kiln; "Since thehottestand most moist air is near the ceiling of the kiln it will be obvious that the outlet flues will be heated near the top of'the kiln. to a higher temperature than their, lower ends;

When the dampers 2-6 are open this difierence in temperature betweenthe upper and lower ends of theflues will cause the air'to flow upwardly in the fluesand be delivered from the kiln, thereby establishing andmaintaining a circulation within the ,kiln.- 7V

' Since it isdesirable to maintain a highde greeof humidity in the kiln during the dry ing operation inorder to prevent case-hardening and checking of the material be- I ing dried, it is desirable "to maintain the requisite circulation without reducing the humidity, and to obtainthis result my outlet flues are extended d0wnwardly to a point substantially level with the bottom of the material being dried. The air, this 7 level in the kiln carries the least moisture so that the air flowing outwardly from-this level through the outlet flues reduces the, humidity a minimum amount for .a given a volume of air circulation.

For some materials it is desirable to increase the rapidity of the air circulation within the kiln and even when drying lumber, after the drying operation has V-been practically completed, it isjdesirable to re- 1 move the air with its entrained moisture and permit the material to cool down before being removed. For the purpose of meeting i-these requirements I have provided myout- .let flues with a pluralityof joints, indi- -cated generally by referencecharacters 25 and 26. WVhile only two joints are shown it will be obvious that a greater numbermay be employed if desired. These joints are formed by hi-nging the sections of the flue together at one side and providingthe opposite with a spring catch which will'hold the sections in alinement in fully extended position for normal operation; When it is necessary or desirable to increase the rapid I ityof the circulation the lower section-of -one'or more of the flues maybe swung up wardly into horizontal position, a shown in full lines on the closest line in the drawings. If still greater rapidity is desired both sections may be swung into horizontal position as shown, in full lines in the middle flue, normally. however, all 'ofthe flu s: Mei

in extended position, as indicated in full lines by the last flue shown and also by dotted lines showing the normal position of the other two flues. The sections of the flues may be swung upwardly by any approved mechanism, but in the present instance I have shown a longitudinally movable rod 27 supported in suitable hangers 28 and corn nected with the lower end of each flue by cables 29. One end of the rod extends outside the kiln and by moving the rod longi tudinally the flue sections may be swung upwardly into horizontal position, as shown in the drawings.

For drying lumber the normal operation of my kiln is substantially as follows: After the kiln has been filled the doors are closed, also the dampers 18 and 26 on the inlet flues and'the outlet flues. Steam is then admitted through the pipe 15 in order that the direct action of the steam upon the lumber will cause the lumber to absorb the heat of the steam and condense the moisture on the outside, from whence it will be gradually evaporated as the lumber becomes thoroughly heated, the thorough moistening of the lumber producing a perfect capillary action from the center which permits the lumber to dry from the center outwardly and prevents case-hardening and checking. After the lumber has been thoroughly moistened and heated the direct steam through the pipe 15 is turned off and heat given off by the steam pipes 11 is relied upon to maintain the requisite temperature. The damper 18 in the inlet flue and the damper 26 in the outlet fiues are now opened so as to establish a circulation of air through the kiln without any direct change from the point of saturation produced by the direct steam to a condition of moist air drying. The percentage of humidity is gradually reduced as the evaporation ceases and the temperature rises. In the last stage of drying the outlet flues are broken at the point near the ceiling permitting a rapid escape of the air and moisture from the kiln at the same time the steam is shut off from the radiating pipes 11 and the inlet flue is left fully open, with the result that the lumber is gradually cooled so as to relieve it of all stress and tension before being removed from the kiln.

It will thus be obvious that I have provided a kiln which is highly efiieient for moist air drying, which thoroughly distributes the air within the kiln so as to uniformly dry all of the material therein and which can be controlled so as to satisfactorily and eificiently meet all of the requirements of successful moist air drying. The details of construction illustrated and described are, of course, capable of considerable modification and variation without departing from the essence of the invention as set forth in the following claims.

I claim: a

1. A drying kiln having heat insulated walls, heating means arranged within said kiln, an outlet flue extending downwardly into the kiln so as to be heated by the surrounding air within the kiln, and means for varying the amount of projection of said flue downwardly into the kiln.

2. A drying kiln having heat insulated walls, heating means arranged within the kiln, and an outlet flue extending downwardly into said kiln, said flue being jointed within the kiln so as to permit the lower end thereof to be swung into inoperative position to thereby reduce the effective length of the flue.

3. A drying kiln having heat insulated walls, heating means arranged within the kiln, and an outlet flue projecting downwardly into-the kiln and provided with a plurality of joints intermediate its ends so that the effective length of said flue may be varied.

4. A drying kiln having heat insulated walls, heating means arranged within the kiln, an air inlet flue disposed within the kiln near the bottom thereof and provided with an air inlet opening outsidethe kiln, and a plurality of discharge branches communicating with said flue and extending upwardly into the kiln, said branches being of gradually increasing length from the intake end of the flue to the opposite end thereof.

5. A drying kiln having heat insulated walls, heating means arranged within the kiln, an air intake flue extending longitudinally of the kiln adjacent one of the lower corners thereof and having an air intake opening outside the kiln, a valve for controlling the supply of air to the kiln through said flue, and delivery branches extending from said flue upwardly into the kiln, said branches being of gradually increasing length from the intake end of the flue.

6. A drying kiln having heat insulated walls, an air intake flue arranged within the kiln and having delivery branches extending upwardly into the kiln gradually increasing distances from the intake end of the flue, a valve for controlling the supply of air to the kiln through said flue, a plurality of outlet fiues extending downwardly into the kiln, said flues being adjustable as to length so as to vary the rapidity of the outflow of air from the kiln, and a controling valve disposed in each of said.outlet fiues.

ELMER E. PERKINS.

Copies 0: this patent may be obtained for five cents each. by addressing the "Gommissioner 0! Patents, Washington, D. 0. 

